Electrical communication



Nov. 15, 1927. 1,649,098

w. L. CARLSON ELECTRICAL COMMUNICATION Filed Se t. 21, 1922 I I I I 4 v4 -za -22 1m Ill! 11/ WENDELL L. CARLSON l l l k l'l'l'k l'l l Patented Nov. 15, 1927.

UNITED STATES) PATENT OFFICE.

WENDELL L. GARLSON, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO RADIO CORPORATION OF AMERICA, OF NEW YORK, N. Y., A CORPORATION 01' DELL WARE.

Application filed September 21, 1922. Serial No. 589,728.

This invention relates to electrical communication and more particularly to amplifieps used in the reception of electrical signa s. The object of this invention is to embody certain new combinations in the construction of a plurality of iron core inter-valve amplifier transformers in a unit of extreme compactness.

A further object is to provide a construction which will greatly reduce the manufacturing cost of a plurality of inter-valve amplifier transformers.

My invention is especially adapted for the use in radio frequency transformers and will be described as such hereiinbut it is ,to be understood that the invention is broad enough to cover audio frequency transformer constructions as well. 1 r

Heretofore it has been customary to construct individual transformers for each stage of a. cascade thermionic vacuum tube amplifier. I propose to assemble the Va.- rious transformer windings of a cascade amplifier all in one iron core shell in such a way that part of the iron magnetic path will be common to adjacent windings.

In other cases where the amplifier is to operate over an extremely wide range of f-requencies, I intend to design the individual windings in the transformer units differently, though employing one shell, and to connect their leads to a suitable switch so as to connect alternately the proper transformer with the amplifier circuit to operate on the particular frequency range it is designed for. In addition to the circuit arrangements described below, still other circuit arrangements employing this transformer are shown in my application Serial No. 30,036 filed May 13, 1925.

Referring to the drawing, Fig. 1 is a. radio receiving circuit employing one radio frequency stage of amplification and a detector tube with three radio frequency transformers each designed to operate over a different frequency range. Fig. 2 is a plan view of three radio frequency transformers disclosing the arrangement of the iron core and windings as employed in Fig. 1. Fig. 3 is a radio receiving circuit employing. three radio frequency stages of amplification and a a detector.

The antenna circuit 1 in Fig. l is coupled to the secondary tuned circuit 2 which connects to the input of the amplifying tube 3. The plate lead of tube 3 connects to a switch arm 11 which makes contact with points 12, 13 and 14 alternately as the arm is rotated at the will of operator. In like manner switch arm 15 is rotated simultaneously with arm 11 to make contact with points 16, 17 and 18. The primary windings of transformers 4, 6 and 8 are connected. at one end respectively to the contact points 12, 13 and 14 and the other ends known as the low potential terminals are connected to a common terminal and to the plate battery 19. The

secondary windings of. transformers 4:, 6 and 8 are connected at their high potential ends to contact points 16, 17 and 18 and their low potential ends are connected commonly to'the filament of detector tube 9. The grid of tube 9 connects through stopping condenser and grid leak unit 20 to the switch arm 15. Telephone receiver 10 is connected in the output circuit of tube 9.

In Fig. 2 the radio frequency transformers 4, 6 and 8 in Fig. 1 or Fig. 3 are shown as they are constructed in the transformer unit. Each individual transformer has its own primary and secondary winding wound on a small laminated iron core plug 21. The laminated iron shell 22, having legs 24, completes the magnetic path around the coils thus forming what is generally lmown as shell type transformers. A certain degree of air gap 23 is usually allowed between core plug 21 and shell 22 so as to reduce the iron losses and regulate the permeability of the magnetic path. In Fig. 3 the tuned antenna circuit is designated by numeral 1 which is coupled to a secondary tuned circuit 2 which in turn connects to the input of the amplifying vacuum tube 3. The output of tube 3 is coupled through the radio frequency transformer 4 to the input of amplifying tube 5. The output of tube 5 is in like manner coupled to the input of the third amplifying tube 7 through the transformer transformers in the construction herein disclosed would create local oscillations in the accompanying Ttube circuits. In practical tests-it has been found that the stray mag netic coupling obtained with such a transformer construction on short wave lengths is practically negligiblein so far as creating local tube oscillations is concerned. If on low radio frequencies or audio frequencies it is found that due to the greater penetration of the magnetic field in the iron that coupling between the adjacent individual transformers creates troublesome efiects, then by properly connecting the adjacent windings of the transformers, i. e., all windings in same direction, the oscillating tendency of the circuit can be eliminated.

The operation of the circuit shown in Fig.

1 is similar to the operation of the circuitshown in Fig. 3 except that only one ampliturns and air gaps 23 between shell 22 andplugs 2l and tby switching to the proper transformer good amplification can be had over the range which the transformer is designed to cover. While one radio stage is shown in this circuit itis obvious that any practical number of stages with a corre: sponding number of transformer units may be employed. 1

Having described my invention, I claim: 1. A transformer element for ether Wave signalling systems comprising a single magnetic shell having a plurality of legs, a plu: rality of magnetic core plugs mounted between pairs of legs of said, shell providing slight, air gaps between the plugs and the windings on each core plug.

2. A transformer element for wave signailing systems comprising a single magnetic core shell having a plurality of legs, anda plurality of transformer primary and secondary windings mounted between pairs of said legs on core plugs providing 'air gaps between the legs and plugs, each transformer being wound and mounted to cover a different band of frequencies.

3. A transformer element for wave signallingsystems' comprising a single magnetic core shell having a plurality of legs,

and a plurality of transformer primary and secondary windings mounted between pairs of said legs on core plugs providing air gaps between legs and plugs,.groups of said transformers being wound and mounted to cover different bands of frequencies.

4. A transformer for wave signalling systems comprising a plurality of primary windings and a plurality of'secondary windings mounted on a common magnetic frame each set of windin s adapted to pass radio frequencycurrents aving a magnetic circuit including an air gap proportioned to increase the. efiiciency'at radio frequencies.

5. A transformer for wave signalling systems comprising a plurality of pairs of primary and secondary windings and separate cores for each pair of said windings, magnetic paths for said pairs of windings having magnetic portions in common for two pairs of windings, each set of windings adapted to pass radio frequency currents having a magnetic circuit including an air gap proportioned to increase the efiiciency at radio frequencies.

6. A high frequency transformer comprising a plurality of pairs of coacting windings, a magnetic core for each pair of coils and a magnetic structure joining said cores comprising a portion of a maghetic path in common for at least two of said pairs of coils, each pair of windings having a magnetic circuit including an air gap proportioned to increase the efliciency at radio frequencies.

7. A transformer comprising a plurality of pairs of coacting windings of different frequency characteristics mounted on a. structure of magnetic material comprising a common portion for the magnetic paths of at least two of said pairs of windings, each air of windings having a'magnetic circuit including an air gap proportioned to in crease the efiicieney at radio fflequencies.

8. A transformer comprising a plurality of pairs of coactin windings of different frequency characteristics mounted on a common core element of magnetic material, each pair of windings having a magnetic circuit including an air gap proportioned to -mcrease the etficlency at radio frequencles. legs, and transformer primary and secondary a closed magnetic clrcuit including at least three legs one of said legs constituting a common magnetic path for said transformers. Y

11. The structure vof claim 10in which the 5 transformer cores are mounted between the legs and at substantially right angles thereto.

12. The structure of claim 10 in which a sli ht air gap is provided. between each core 10 an leg.

13. A transformer core for ether wave signalling systems comprising a single shell 0 magnetic material having a plurality of legs and a plurality of cores of magnetic material mounted between said legs, the axes of said cores being, in substantial alignment whereby substantially balanced mag-- netic circuits are provided.

- WEN'DELL L. GARLSON. 

